1. Field of the Invention
The invention relates to an apparatus for moving a printer carriage for printer units, in particular for teleprinters and typewriters, in which the feed and return movements are produced by a drive motor having a reversible direction of rotation.
2. Prior Art
In printer units for teleprinters and typewriters, the printer carriage is generally moved along the platen to print-out individual characters. After print-out of the last character in a row, the printer carriage is returned in the shortest possible time to the beginning of the row. The printer carriage is moved in the forward or feed direction by a drive motor which constantly rotates in one direction and also tensions a carriage return spring. During the carriage return, the drive motor is cut off from the printer carriage at a coupling and the carriage return spring moves the carriage back to the beginning of the row where it is stopped by a shock absorber.
To mechanically simplify such carriage drives, the printer carriage, which slides on guide bars, has been secured to a toothed belt which is driven by a gear stage in the return direction by an electronically controlled d.c. motor having a reversible direction of rotation (see German Offenlegungschrift No. 2,263,283). The mechanical components of carriage return spring, shock absorber, and coupling can then be dispensed with. This type of drive with a d.c. motor has the disadvantage however, like any servo-drive arrangement, that rapid and accurate positioning of the printer carriage requires a costly feedback circuit, with scanning of each position of the carriage and an adjustment of the motor via such feedback circuit until a desired position is reached.